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Minor improvement on device syncer #231

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merged 5 commits into from
Jan 16, 2024
Merged

Minor improvement on device syncer #231

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96cd1cc
Minor improvement on device syncer
chhwang Dec 6, 2023
c1f3f2b
tackle comment
chhwang Dec 24, 2023
71c8fda
Merge branch 'main' into chhwang-patch-1
chhwang Dec 24, 2023
23d72ee
Merge branch 'main' into chhwang-patch-1
chhwang Dec 24, 2023
61ea81a
Merge branch 'main' into chhwang-patch-1
chhwang Jan 15, 2024
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21 changes: 8 additions & 13 deletions include/mscclpp/concurrency_device.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
#ifndef MSCCLPP_CONCURRENCY_DEVICE_HPP_
#define MSCCLPP_CONCURRENCY_DEVICE_HPP_

#include "atomic_device.hpp"
#include "poll_device.hpp"

namespace mscclpp {
Expand All @@ -29,19 +30,13 @@ struct DeviceSyncer {
if (threadIdx.x == 0) {
// Need a `__threadfence()` before to flip `flag`.
__threadfence();
int tmp = isIncFlag_ ^ 1;
if (tmp) {
if (atomicInc(&count_, maxOldCnt) == maxOldCnt) {
flag_ = 1;
}
POLL_MAYBE_JAILBREAK(!flag_, maxSpinCount);
unsigned int tmp = preFlag_ ^ 1;
if (atomicInc(&count_, maxOldCnt) == maxOldCnt) {
atomicStore(&flag_, tmp, memoryOrderRelaxed);
} else {
if (atomicInc(&count_, maxOldCnt) == maxOldCnt) {
flag_ = 0;
}
POLL_MAYBE_JAILBREAK(flag_, maxSpinCount);
POLL_MAYBE_JAILBREAK((atomicLoad(&flag_, memoryOrderRelaxed) != tmp), maxSpinCount);
}
isIncFlag_ = tmp;
preFlag_ = tmp;
}
// We need sync here because only a single thread is checking whether
// the flag is flipped.
Expand All @@ -51,11 +46,11 @@ struct DeviceSyncer {

private:
/// The flag to indicate whether the barrier is reached by the latest thread.
volatile int flag_;
unsigned int flag_;
/// The counter of synchronized blocks.
unsigned int count_;
/// The flag to indicate whether to increase or decrease @ref flag_.
int isIncFlag_;
unsigned int preFlag_;
};

} // namespace mscclpp
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